Raman Laser Switching Induced by Cascaded Light Scattering

It is shown that, in multimode Raman lasers, cascaded light scattering (CLS) not only extends the optical frequency range, but can also modulate the laser dynamics. The origin of this phenomenon lies in the fact that many Raman lasing modes are directly correlated through CLS. The coupled-mode equations only describe single-mode cascaded Raman lasers and are insufficient for describing the multimode case. In this work, additional terms are introduced to account for intermodal interaction and, therefrom the physical mechanism behind the mode-switching phenomenon is revealed. Additionally, mode-switching controlled solely by a single-mode pump in a whispering gallery mode (WGM) silica Raman laser is demonstrated. As the intracavity pump power is increased, laser switching happens between two adjacent WGMs in the same mode family.